1. Field of the Invention
The invention relates to an auxiliary drive system for a power-driven apparatus, such as a power-driven shutter mechanism, having an actuator and movable members driven by the actuator, and, more particularly, to an auxiliary drive system for running in a power-driven apparatus which is used after it has been left dormant for a long period of time.
2. Description of Related Art
Typically, photographic cameras are equipped with shutter mechanisms which includes shutter blades operative to open and close to control an exposure time. Some types of cameras, such as compact cameras and instant cameras, are equipped with programmed shutter mechanisms in which aperture blades are operative for both diaphragm and shutter. For example, a programmed shutter mechanism, on which both the shutter speed and F-number are set automatically according to the brightness of a subject to be shot, typically has more-than-two shutter blades which are opened and closed all at once by an actuator such as a motor and a solenoid. In this programmed shutter mechanism a shutter speed or a time interval for which the shutter blades remain open is determined according to an exposure value and a size of the aperture, which corresponds to F-number, depends upon shutter speeds.
By the way, the shutter mechanism may behave precariously due to a change in the coefficient of friction among the shutter blades, a change in the coefficient of friction of mechanical parts or members of a shutter drive mechanism, a change in viscosity of a lubricant of the shutter blades when operating the camera after having left it dormant for a long period of time. In such the case, the shutter speed of the shutter mechanism or both the shutter speed and aperture of the programmed shutter mechanism will be imprecise, which causes under or over exposure. The same problem occurs in various mechanisms equipped with movable members like shutter blades. For example, a camera equipped with an automatic focusing feature encounters difficulties in smooth movement of a focusing lens element of the taking lens with an effect of loosing the chance to losing the chance to shoot a subject due to a delay in operation of the shutter blades which should occur after conclusion of focusing the taking lens or an effect of forming an out-focused picture. Further, a printer equipped with a paper feed roller or rollers encounters an occurrence of an imprecise image printed on a paper due to an uneven feed speed if irregular rotation of the paper feed rollers is caused.
It is therefore an object of the invention to provide an auxiliary drive system for a power-driven apparatus having movable members which prevents the movable members from encountering unstable movement.
According to one aspect of the invention, the auxiliary drive system for a power-driven apparatus having an actuator and movable members driven by the actuator comprises control means for controlling the actuator to force the movable members to cause predetermined movement along a fixed axial distance so as thereby to run in the movable members in response to either loading the power-driven apparatus with a battery as a power source or powering on the power-driven apparatus.
According to another aspect of the invention, the auxiliary drive system for a power-driven apparatus having an actuator and movable members driven by the actuator comprises timer means for counting a time since the last movement of the movable members and control means for controlling the actuator to force the movable members to cause predetermined movement so as thereby to run in the movable members when the timer has counted a predetermined time since the last movement of the movable members.
According to an preferred embodiment, the control means may control the actuator to force the movable members to cause the predetermined movement for running-in operation of the movable members in response to loading the power-driven apparatus with a battery or batteries as the power source. Further, the control means may further control the actuator to force the movable members to cause the predetermined movement for running-in operation of the movable members in response to powering on the power-driven apparatus. The control means may permit the actuator to force the movable members to cause the predetermined movement for running-in operation of the movable members only while the power-driven apparatus is powered with battery power higher than a predetermined level.
According to another aspect of the invention, the auxiliary drive system is employed as one for a power-driven shutter system, such as a programmed shutter, as the power-driven apparatus which comprises a pulse motor and a shutter blade or blades driven by the pulse motor in response to shutter release to make exposure on a photographic film while the shutter blades move from an initial position to a position beyond an opening position in which the shutter blades are on point of starting the exposure and return to the initial position. The control means controls the pulse motor to force the shutter blades to cause predetermined back and forth movement between the initial position and a position before the opening position so as thereby to run in the shutter blades. The pulse motor may be desirably operated with a lower kinetic energy during running-in operation of the shutter blade than during exposure operation of the shutter blades.
With the auxiliary drive system of the invention, because the running-in operation between the fixed axial positions of the movable member is performed in response to powering on either the power-driven apparatus having a movable member driven by the actuator or the machine equipped with the power-driven apparatus, to a lapse of a predetermined period of time since the last movement of the movable member, or to loading either the power-driven apparatus or the machine equipped with the power-driven apparatus with a battery or batteries, the given coefficient of friction between the movable members and the given condition of lubrication are favorably maintained even after the power-driven apparatus has been left dormant or suspended with the result of having the power-driven apparatus operate stably.